Radially expandable stent IV

ABSTRACT

A radially expandable support structure is presented, for keeping open lumina within a body, in particular a blood vessel, having a tube-shaped structure that has at least two partial structures, with a wall surface that extends between a first and a second end, which has several cut out areas, in particular, slits, which are essentially oriented parallel to the longitudinal axis of the tube-shaped structure. At least one of the partial structures ( 11 ) extend without interruption in the axial direction generally from the first end to the second end of the tube-shaped structure. A first partial structure ( 1, 2 ) can be expanded at least in the radial direction and has at least one radial-expansion component. The individual radial expansion components ( 12, 13 ) are arranged as a helix or in a helix shape. A second partial structure ( 11 ) is generally almost rigid in the axial direction. The two partial structures ( 1, 2; 11 ) are arranged in such a way that during the radial expansion of the tube-shaped structure, the second partial structure ( 11 ) receives the longitudinal axial forces that arise.

BACKGROUND OF THE INVENTION

The invention involves a radially expandable support structure forkeeping open lumina within a body, in particular a blood vessel.

EP 0 335 341 B1 discloses, among other things, an expandableintraluminar vascular structure or prosthesis having at least one thinwalled tube-shaped part with first and second ends and a wall surfacearranged between the first and second ends, which has essentially thesame thickness and several slits, which are directed essentiallyparallel to the longitudinal axis of the tube-shaped part. Thetube-shaped part can have a first diameter, which makes theintraluminary transport of the tube-shaped part into a body passage thathas a lumen possible, and the tube-shaped part can have a second,expanded and deformed diameter; such that a force directed radiallyoutwardly can be applied from inside of the tube-shaped part and thesecond diameter is variable and depends on the amount of the forceacting on the tube-shaped part, whereby the tube-shaped part is expandedand deformed in order to expand the lumen of the bodily passage. Thevascular structure or the vascular prosthesis has several tube-shapedparts and at least one connection piece, which is arranged betweentube-shaped parts that border each other, in order to connecttube-shaped parts, which are bordering each other, together with eachother in a flexible manner.

A disadvantage in this intraluminary vascular structure is therelatively high radial rigidity of the individual parts, whichnoticeably impairs the flexibility necessary in a lumen for theprevention of internal injuries.

In U.S. Pat. No. 4,969,458, an intraluminary support structure isdisclosed, which is made up of a spiral-shaped spring. Disadvantageousin this is the relatively high radial instability, which can lead topositions of undesired buckling.

SUMMARY OF THE INVENTION

From the aforementioned stems the problem of at least partiallyeliminating the disadvantages mentioned above using a new type ofsupport structure. The resulting problem lies in particular in ensuringa high stability in the longitudinal direction with not too small of aradial rigidity, while avoiding a shortening of the support structureduring radial expansion and while avoiding uncontrolled radial bucklingmovements.

This problem is solved according to the invention by a support structureaccording to the present invention.

The support structure according to the invention has a tube-shaped bodythat has at least two partial structures, with a wall surface thatextends between a first and a second end, which has several cut outareas, in particular, slits, which are essentially oriented parallel tothe longitudinal axis of the tube-shaped body. At least one partialstructure runs without interruption in the axial direction almost, atleast, from a first end to a second end of the tube-shaped structure.The first partial structure can be expanded at least in the radialdirection and has at least one radial-expansion component, where theindividual radial expansion components are arranged as a helix or in ahelix shape. The second partial structure is almost rigid in the axialdirection. The radial expansion component can be constructed to beclosed, for example, oval, rectangular, rhomboidal, or elliptical inshape, or open, for example, in a meandering shape.

Through in particular this arrangement of the partial structures, it isachieved that during the radial expansion of the tube-shaped body, thesecond partial structure receives the thereby arising longitudinalforces. This has the result that the radial deformation is independentof the axial deformation and accordingly no shortening in thelongitudinal direction occurs during the radial expansion. This isespecially important during the invasive surgery, in order to create adesired supporting effect over a certain length.

In an advantageous manner, at least one partial structure has at leastone meandering pattern, in order to increase the flexibility. Thisapplies for the at least two partial structures.

It is advantageous that the loops of the meandering pattern are ofvarying sizes. This involves the elongation (amplitude) and/orwavelength, both in the radial as well as in the longitudinal directionof the support structure. Thus, on the whole a highly homogenousexpandability relative to the first partial structure arises.

Furthermore, it is advantageous that the meandering pattern is a doublemeandering pattern, in order to increase the radial expandability.

The double meandering pattern is made advantageously of a firstmeandering pattern having loops and a second meandering pattern havinglarger or smaller loops than that of the first meandering pattern, inorder, in this manner, to achieve at least an approximately uniformexpansion during loading to cause radial expansion.

Furthermore, in an advantageous manner, a connection element thatconnects to the respective longitudinal end of the first radialexpansion component is constructed as a loop-shaped stay. The stayprevents or lessens the possibility of the loops becoming spaced apartor rising out of the surface of the support structure when bending isrequired. Furthermore, when expanded, they improve the support action ofthe stent via a uniform surface.

In addition, it is advantageous when the wall surface has an essentiallyuniform thickness, in order to improve the homogeneous radial expansion.

The support structure can, for example, be made of a stainless steelthat is suitable for medical purposes and/or have a biocompatiblecoating. Furthermore, any biocompatible material can be used as amaterial for manufacturing the stent, for example, tantalum, platinum,niobium, alloys and synthetic materials. The structures can bemanufactured by laser cutting, electro-erosion, etching or even metalcutting.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofthe preferred embodiment of the invention, will be better understoodwhen read in conjunction with the appended drawings. For the purpose ofillustrating the invention, there is shown in the drawing an embodimentwhich is presently preferred. It should be understood, however, that theinvention is not limited to the precise arrangements andinstrumentalities shown. In the drawings:

FIG. 1 is an unrolled support structure.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows the unrolled, wall surface of a support structure. This hasa first partial structure 1, 2 that includes double meanderingstructures made up of meandering structures 12 and 13 and a secondpartial structure 11. The meandering structures form several slits 6, 7,8, 9, which are directed essentially parallel to the longitudinal axisof the tube-shaped body 3. The second partial structure 11 runs withoutinterruption in the axial direction almost from the first end 4 to thesecond end 5. The first partial structure can be expanded in the radialdirection and has a radial expansion design element, which is made up ofthe radial expansion components 12, 13. These are arranged as helixes.The second partial structure 11 is relatively rigid in the axialdirection in spite of the loop-shaped progression.

Furthermore, the connection element 10 that connects to the longitudinalends of the radial expansion component 12, i.e. in this case on the loopends of the first meandering pattern 12, is constructed as a loop-shapedstay.

The stent depicted as an example has a length of approx. 15 mm and aradial circumference of approx. 4 mm. The helix angle α of the helixamounts to approximately 50° relative to the longitudinal direction ofthe support structure.

With this exemplary embodiment of the support structure according to theinvention, excellent results are achieved.

What is claimed is:
 1. Radially expandable support structure for keepingopen a lumen within a body comprising: a tube-shaped body having twopartial structures, the tube-shaped body having a wall surface extendingbetween a first and a second end of the tube-shaped body, the wallsurface having several cut out areas essentially oriented parallel to alongitudinal axis of the tube-shaped body, the at least two partialstructures including a first partial structure (1, 2) being expandableat least in a radial direction and having at least one meanderingpattern as a radial-expansion component, wherein individualradial-expansion components (12, 13) directly connected to each otherfrom the first end (4) to the second end (5) of the tube-shaped body arearranged in an almost helical shape, and a second partial structure (11)being substantially rigid in an axial direction and extending withoutinterruption in the axial direction generally from the first end to thesecond end of the tube-shaped body, the second partial structure (11)also having at least one meandering pattern, a portion of the secondpartial structure (11) being integral with the first partial structure(1, 2) intermediate the first and the second end of the tube-shapedbody, the first and second partial structures (1, 2; 11) being such thateach radial-expansion component (12, 13) radially succeeds a secondpartial structure (11) and that the second partial structure (11)receives longitudinal axial forces that arise during radial expansion ofthe tube-shaped body, wherein the radial deformation is independent fromthe axial deformation and no shortening in the longitudinal directionoccurs during the radial expansion.
 2. Support structure according toclaim 1, wherein the loops of the meandering pattern are of variablesizes.
 3. Support structure according to claim 1, wherein the meanderingpattern is a double meandering pattern.
 4. Support structure accordingto claim 3, wherein the double meandering pattern of the first partialstructure (1, 2) consists of a first meandering pattern (12) with loopsand a second meandering pattern (13) with larger or smaller loops incomparison to the loops of the first meandering pattern.
 5. Supportstructure according to claim 4, wherein at least one connection designelement (10), connected to respective longitudinal ends of the firstmeandering pattern (12), is constructed as a loop-shaped stay. 6.Support structure according to claim 1, wherein the wall surface has anessentially uniform thickness.
 7. Support structure according to claim2, wherein the meandering pattern is a double meandering pattern.